A. Field of the Invention
This invention relates to ultrasonic diagnostic systems such as those used in the medical field and, more particularly to the displaying of the ultrasonically derived information. More specifically, this invention provides both a technique and apparatus for the video displaying of the A-trace.
The A-trace is the graphically-depicted information derived from the ultrasonic pulse-echo emerging from the examined body. As is known in the art, pulse reflections occur when the ultrasonic transmitted pulse, transmitted into the examined body via a transducer, encounters a discontinuity in media defining the propogation path. The magnitude of the reflection is proportional to the difference in the media densities. The echo amplitude is typically graphically represented as the ordinate value, while the echo return time (indicative of body depth) is reproduced on the abscissa. Accordingly, one may, by viewing the A-trace, determine the depth into the body of each discontinuity in the pulse-propogation path and the type of media transition. With one's knowledge of the theoretical internal structure of the body (or, in the case of medical diagnostics, the human physiology) one may identify the locations of various structural components (or organs).
B. Summary of the Prior Art
Conventional ultrasonic systems have employed oscilloscopes as the A-trace display means. Earlier systems employed two oscilloscopes, the second of which was dedicated to the display of images derived by subjecting the pulse-echo signal to one of several known signal-processing techniques. The oscilloscope possessed several inherent weaknesses, however, which led to the subsequent use of TV monitors for displaying the processed image. First, oscilloscopes offered poor display visability. Secondly, oscilloscopes having storage capability were expensive. Thirdly, oscilloscopes cannot provide highly desirable alphanumeric information, such as patient-identifying data. Additionally, the use of a TV monitor permitted the use of video tape, and the ability to drive several monitors from a single source, both of which are economically beneficial. The A-trace, however, continued to be displayed on an oscilloscope, necessitating the use of two display devices. If permanently recorded images were desired, two cameras, or alternately, a single relocatable camera, were necessary.